With the increasing cost and decreasing availability of petroleum and natural gas, greater emphasis is being placed on the use of coal as a source of energy. Several processes have been developed whereby coal can be converted to a variety of liquid and gaseous products useful as fuel or as feedstocks for chemical conversion to other desired products. In any such process, however, a serious problem which must be overcome is the disposition of large amounts of ash, representing the inorganic constituents of the coal, which has little or no economic value. In addition, and particularly in the case of coal containing relatively large amounts of sulfur, the sulfur-containing gases, such as SO.sub.2, SO.sub.3, and H.sub.2 S which are formed in the process present serious problems with respect to corrosion of equipment or pollution of the atmosphere. While these problems can be solved by the use of special corrosion-resistant equipment and by treatment of effluent gases to remove sulfur compounds, these expedients increase the cost of any process for utilizing coal in this manner and render the economics unfavorable in comparison to the use of petroleum-based products or natural gas.